Method for fault detection in a plasma process

Abstract

A method of fault detection is described for use in a plasma process chamber powered by an RF source and subject to periodic standard preventive maintenance. Prior to a production run, the changes in magnitude of a plurality of Fourier components of the RF source resulting from known changes in a plurality of process conditions are determined and a single parameter which is a linear combination of a selected subset of said components is constructed. The construction is such that the combination is relatively sensitive to pre-selected process changes and relatively insensitive to said standard preventive maintenance. Then, during the production run, the single parameter is monitored to determine if there is a fault in the plasma process.

What is claimed is:  
     
       1. A method of fault detection in a plasma process chamber powered by an RF source and subject to periodic standard preventive maintenance events, comprising the steps of: 
       prior to a production run using a predetermined plasma process, determining the changes in magnitude of a plurality of Fourier components of the RF source resulting from known changes in a plurality of process conditions and constructing a single parameter which is a linear combination of a selected subset of said components, said combination being more sensitive to pre-selected process changes than to said standard preventive maintenance events,  
       running the plasma process during a subsequent production run, and  
       during said production run, monitoring said single parameter to determine if there is a fault in the plasma process.  
     
     
       2. A method as claimed in  claim 1 , wherein the changes in process conditions include variations in the process input parameters. 
     
     
       3. A method as claimed in  claim 1 , wherein the changes in process conditions include induced faults in the process. 
     
     
       4. A method as claimed in  claim 3 , wherein the induced faults include hardware faults. 
     
     
       5. A method as claimed in  claim 1 , wherein the pre-selected process changes affect the yield of the process. 
     
     
       6. A method as claimed in  claim 1 , wherein the Fourier components are those of the voltage, current and phase of the RF power signal.